What cup size do you need 42 inch bust?

To determine the cup size for a 42-inch bust, you also need to measure the band size, which is typically taken just under the bust. For example, if the band size is 36 inches, the difference between the bust measurement (42 inches) and the band measurement (36 inches) is 6 inches. This difference corresponds to a cup size of F. However, cup sizing can vary between brands, so it's best to try on different sizes for the best fit.